A prior art plug gage is disclosed in U.S. Pat. No. 4,058,901 to Lendi et al. The plug gage disclosed utilizes balls to engage the surfaces to be dimensioned. The three balls are housed by crimping in a guide channel which passes through the wall of a housing. Within the housing, the balls rest against a conical part which is centered on the axis of the housing. As the balls move inwardly during dimensioning, the conical part is urged upwardly. A rod connected to the conical part transmits axial movement to a transducer system such as an electronic sensor or a comparator. With this system, a slight rotation of the conical part results in different surface portions being presented to the balls. If the conical part is imprecisely machined, surface deviations may affect the repeatability and accuracy of measurements.